Plant Growth Accelerated Tremendously With LEDs

Plants compared side-by-side, with LED-illuminated plants growing way more than the sunlight-illuminated plants

[GreatScott!] was bummed to see his greenhouse be empty and lifeless in winter. So, he set out to take the greenhouse home with him. Well, at least, a small part of it. First, he decided to produce artificial sunlight, setting up a simple initial experiment for playing with different wavelength LEDs. How much can LEDs affect plant growth, really? This is the research direction that Würth Elektronik, supporting his project, has recently been expanding into. They’ve been working on extensive application notes, explaining the biological aspects of it for us — a treasure trove of resources available at no cost, that hackers can and should learn from.

Initially, [GreatScott!] obtained LEDs in four different colors – red, ‘hyper red’, deep blue, and daylight spectrum. The first three are valued because their specific wavelengths are absorbed well by plants. The use of daylight LEDs though has been controversial.  Nevertheless, he points out that the plant might require different wavelengths for things other than photosynthesis, and the daylight LEDs sure do help assess the plants visually as the experiment goes on.Four cut tapes of the LEDs used in this experiment, laid out side by side on the desk

Next, [GreatScott!] borrowed parts of Würth’s LED driver designs, creating an Arduino PWM driver with simple potentiometers. He used this to develop his own board to host the LEDs.

An aluminum PCB increases heat dissipation, prolonging the LEDs lifespan. [GreatScott!] reflowed the LEDs onto it with solder paste, only to find that the ‘hyper red’ LEDs died during the process. Thankfully, by the time this problem reared its head, he managed to obtain the official horticulture devkit, with an LED panel ready to go.

[GreatScott!’s] test subjects were Arugula plants, whose leaves you often find on prosciutto pizza. Having built a setup with two different sets of flower pots, one LED-adorned and one LED-less, he put both of them on his windowsill. The plants were equally exposed to sunlight and equally watered. The LED duty cycle was set to ballpark values.

The results were staggering, as you can see in the picture above — no variable changing except the LEDs being used. This experiment, even including a taste test with a pizza as a test substrate, was a huge success, and [GreatScott!] recommends that we hit Würth up for free samples as we embark on our own plant growth improvement journeys.

Horticulture (aka plant growing) is one of the areas where hackers, armed with troves of freely available knowledge, can make big strides — and we’re not even talking about the kind of plants our commenters are sure to mention. The field of plant growth is literally fruitful and ripe for the picking. You can accomplish a whole lot of change with surprisingly little effort. The value of the plants on your windowsill doesn’t have to be purely decorative, and a small desk-top setup you hack together, can easily scale up! Some hackers understand that, and we’ve started seeing automated growing solutions way before Raspberry Pi was even a thing. The best part is, that you only need a few LEDs to start.

We thank [MendesL] for sharing this with us!

37 thoughts on “Plant Growth Accelerated Tremendously With LEDs

    1. You can find them, you’ll just pay a lot more. I bought then overpriced, compared to on eBay, Arduino Nano V3.0 clones on Amazon for $5.99 each shipped. Now, they’re $49.99 for three!

    2. A lot of folks (like myself) have also bought a ton when they were cheap with delusions of grandeur of becoming hacking masters… Then quickly lost them in the “abandoned hobby” drawers lol. But with world slowed down a notch, we’re digging them up again. 😅

    1. (…especially if you plan arugula seeds, says the smartass in the back row there. Don’t worry, I’d never plant arugula. It’s right up there with kale in the “not food” category.)

    2. Running solar and off grid, no way can you even guess cost. However a years worth of food for 4 might suck an entire installations output. They do this in Greenland from thermal generation so not sure if there’s new innovation

      1. What?
        Your off grid solar wasn’t paid for?
        Seems like cost is _easy_ (unless you don’t like answer), only question is life of components.

        Food for one would require a large installation. 1/4 acre per rabbit food eater is a rule of thumb I recall from somewhere. Much more if you want to feed the vegetables to food, then eat them.

        Greenland doesn’t grow it’s own wheat. They are topping off fresh veg in winter.

    3. Tjere are towns here in the netherlands where it does not get dark at night. They are surrounded by huge areas covered with greenhouses, completely flooded with artificial light to grow tomatoes, strawberrys and what not.

  1. >[GreatScott!] recommends that we hit Würth up for free samples as we embark on our own plant growth improvement journeys.

    WE have so far been very generous, and they offer products with proper documentation (datasheets, CAD, EDA and spice models) at very reasonable prices when you buy from them directly, but please … when you decide to interact with companies like these, consider it part of building a business relationship. Don’t just go for the loot.

    That said, I find AlboPepper on youtube to be an excellent channel. The guy is running lots of experiments to science the heck out of indoor farming and horticultural LED lighting.
    Here’s a related selection of videos:

    1. I openly contacted Wurth within 24 hours of that video, even if you are a light related business they have to charge you somewhere in the range of 300-400 euro. Had a nice chat with their salesperson though!

    1. LED grow light enthusiasts _never_ grow with HPS on the left, LED on the right.
      Because when they do, the plants all grow towards the HPS and the LED plants are relatively stunted. Pot growers did the experiment, many times by now.

      More basically, growing under lights is the most un-green thing anybody can do.
      Outdoor free light from the worlds greatest sun. Also squared cubed law. light intensity at top of plant same as at bottom because sun so far away (ignore self shading).
      Indoor, burn coal to power electric light. Top of plant 1 foot from sun, bottom of plant 4 feet from sun.

      Pot is effectively legal everywhere in the USA. The markets are all glutted with quality outdoor from near ideal environments. Say no to your local indoor, buy CA buds on grey market. Profit!

      I grew indoor for 20 years. Have now been growing outdoor for another 20. Indoor was for jail avoidance.

      Six outdoor plants, CA central valley. I have to smoke a 1/2 ounce/day or I’m falling behind. Woe is me.

      1. Very much depends on how you are ‘growing under lights’ – if its supplemental lighting for your greenhouse, so those late winter and early spring days can be much more productive, perhaps extending the growing day in general then it might well be the MOST green thing you can do, as it makes that little patch of land right where you are produce more/everything you need…

        If you are growing under lights in a basement with no natural light its still plausible you can make it greener than growing outdoors – but that would be very climate related – for instance if its really really damn cold outside for much of the year then being those few meter down and thus passively warm enough may well end up greener than shipping stuff, and as there is no way you can grow outside at the time… Its probably the greenest method, though if you really need fresh, or to live there etc is another question entirely.

        1. Antarctica is an edge case.

          Everywhere else, ship it in. Maybe Greenland, but if it has access to the sea and docks, freeze and ship it.

          Anywhere with a growing season? It’s not even close.

          1. Up north herein Canada, food can be expensive by the time it gets there. Shipping iys expensive. And weather can impact delivery.

            So there is talk of greenhouses to supplement what’s shipped, for food independence.

            Of course, the real problem is that people who lived off the land were made to “go European” in housing and food, and that’e the initial problem

          2. Even when you have a growing season transport, potential land clearances, and water consumption (etc) to grow it where the seasons are longer, climate is better for x or y can have very significant costs, both economically and ecologically.

            And depending on how your source the electricity for your grow lights they can work out very very green on that front anyway – its not all burn coal as you suggest.

            Even if it was if you use growlights to increase your local yield by say 20% as you extend the growing season, that is still energy burnt in a giant and very efficient and clean burning power station (processing exhaust gas from a giant static burner is very trivial compared to mobile combustion), transmitted with good efficiency, and then converted to light with pretty good efficiency too. Where shipping in produce from somewhere that can grow more like perhaps Spain with their giant fields of plastic greenhouse you require so much transport infrastructure, and if you transport it with diesel and marine fuel oils (which is currently almost certain) you are burning inefficiently and very much dirtier than the coal power station, and needing to invest lots of energy to refine and transport the fuel too… If its frozen there is a constant energy cost to keep it there, and then you have to account for spoilage, as any transportation is certain to spoil some percentage of the import, and long distance its going to be so much worse than from just next door.

            Its not cut an dry by any stretch that artificial lighting is greener or not, but its far more in the running than you seem to think.

          3. Also its not just cold conditions – you have a nice closed basement system in horrible hot arid climate and you can grow so much without wasting that rare resource water, and probably use the power of the sun and a few battery to run the lights longer…

            There are so many places on Earth where a city/town type life can’t be supported by local agriculture easily if at all, where shipping is expensive and challenging. Yet many of those places are worth maintaining the city and town in – as rare mineral mines are there for instance.

            Also the lifestyle of education and mental development we have all been able to enjoy comes from having more settled reliable food supply and situation – None of us could get on with learning much beyond bushcraft skills without stable agriculture, as you have to apply those skills so continually to survive, there just isn’t time to read through the Man page, learn how to type – maybe even no learning how to read! Yet you can’t grow and ship everything from where the conditions would be good – that leads to stupidity like slash and burn rain-forest farms, that are fertile for all of 4 mins, and take stupidly long times to recover…

          4. Unless it’s a cold environment, double the power used to cool the space, maybe more. Depends on light efficiency of course, but in any case almost 100% of energy will end as heat.

            Solar power is not free. It is not free of environmental cost. To hang you argument of imaginary perfect power plants is just _dumb_.
            Hydro power is virtually all ‘spoken for’, there is so much water going down the hill every year. If you use it for grow lights, later fuel will be burnt.

            In practice, it’s not remotely close. Name one legal commercial food crop grown under lights?

            Extending growing seasons is almost always done with decomposing shit (for heat) or powerplant waste heat and greenhouses (The Dutch invented modern vegetable gardening).

            Light to force/retard flowering is for flowers (including those that are smoked).

            Eat 90% what’s in season or what stores well. Ocean shipping is amazingly efficient though.
            If you live on the tundra, learn to like Vodka, Caribou, Whale and Seal. But protip…move to were the food is (/ Kinison)

            20% yield boost with supplemental lights? Could be possible, but I smell a stat pulled from a dark smelly place. Cite?

          5. Go down a few meter HaHa and you need no energy to cool a space, temperatures under the surface are pretty stable and consistent year round, and in most places just about right at that few meters for almost any food plant to grow in.

            Yes you need heat, and waste heat is good – but the plant still can’t grow without light, so having lights on for those cloudy day, early morning and evening – extending the best growing season in your green house – so weeks before you could really grow anything without you have a crop, and weeks after they days have grown too short they would be still able to produce a serious crop.

            Also never said solar was free of environmental costs, but you build it and 30, 40 maybe even more 100 years later, as the degradation on current processes is very very low the panels are still working just fine – effectively the panels are all prepaid electric for ages, and at pretty low environmental cost, even in the short term, so if you look after them so they can last… I’d go as far as to say its basically cost free, as over those decades the already pretty small upfront cost is spread very very thin, to the point it becomes a rounding error…

            20% was indeed a fairly random number – but as with some work you can easily get 3 or 4 big yield crops a year in controlled environment where outside or with just a passive greenhouse you probably only get 1 or maybe 2 – so even a 300% yield increase isn’t at all implausible. It would just cost more energy!

            Where feeding in that extra trickle to your greenhouse can boost the plant growth while still getting much of the energy directly from the sun, so giving a 20%, 30%, 40% – some relatively marginal improvement is pretty trivial, and requires very little extra energy, as in that sort of situation you don’t have the lights on in the greenhouse except when the weather is poor for plant growth…

            There are leafy greens – the salad leaves type things grown under lights commercially in various places, including in some disused tunnels of the London Underground (last I heard at least they were still running).

      2. @HaHa said: “Outdoor free light from the worlds greatest sun.”

        Which “world”? Earth?

        @HaHa said: “Pot is effectively legal everywhere in the USA.”

        No it’s not. In-fact pot is actually against Federal law, therefore it is illegal everywhere in the U.S. Buy a gun anywhere in the U.S. and lie on your ATF Form 4473 about not using drugs. That’s looking for serious trouble!

  2. I replaced my ancient fluorescent grow lights with a commercial LED fixture this year. The results were surprising as my tomato plants were begging to be planted out weeks earlier than usual. I will have to delay starting seeds next year.

    Seeds were started on 19 Jan. or a little more than 2 months prior to the usual time to set out around here. From my notes I was getting worried by 18 Feb. With a favourable forecast, they went in the ground on 14 Mar. With fruit already set on.

    The tomatillos also liked the new lights.

  3. You could have done so much more…how many hours were lights on? 24 hours? How about 16 hours versus 20 vs 24? What about distance of light source from top of plant? Usually grow light need to be really close to top of plant? I’d also control with bottom up watering and consider a box with reflective aluminum foil to maximize light exposure

  4. “Arugula plants, whose leaves you often find on prosciutto pizza.” What language is this? Is it something people eat in big cities? Something they smoke? Weave into baskets? Metric food?

  5. “we’ve started seeing automated growing solutions way before Raspberry Pi was even a thing”
    That’s the most smoothie hipster thing I’ve heard in a long time.
    Like, really? Automated growing solutions were build with discrete components for decades. Even better, you could build a fully mechanical automated growiing solution if you wish, with only electrical thing is lighting.
    Come on. Now Raspy is a measure of backwardness.

    1. Virtually all food production started off as an automated process. The only manual stage was the harvest that required foraging and gathering 🤣.

      But yeah, rainbird automatic watering, discrete timers, relays, and PIDs have been common for decades. Then there are all the self watering “hacks” that date back thousands of years. Artificial lighting is a pretty old technology as well by modern standards and even the use of specific Leads targeting certain wavelengths is at least a decade old in the diy/consumer space.

  6. I did some experiments with hydroponics a few years ago, in an office with windows that didn’t get good sunlight. I used some LED grow bulbs from Wallmart, and I used arugula as my crop. The results were pretty awesome. I actually assumed the fast growth was mainly due to the hydroponics, but this is making me rethink that. Once I’m able to resume my experiments, I’ll have to explore this more!

    1. Ohhh I know this one!

      They probably look like fruit flies. They aren’t fruit flies, they are are tiny mosquitoes.

      It’s caused by your ground being too moist, which attracts them. They lay eggs which then produce larvae that eat anything under the ground, including the roots of the plants.

      There are several routes that you can take to solve this. My preferred methods are:

      1. water from underneath. You can buy and/or make your own system. This is super nice to have, even if you don’t have this problem. You can buy them pre made or build your own. What is is, is a bucket that goes to the top, with a bucket inside it (bucket can be anything you like). The bottom of the inside one is higher than the lower one. Put a tube in that goes to the bottom one so you can dump water in there. The top one shouldn’t touch the water. Cut a piece of cloth, if possible thick felt, but cotton should work just as well, that goes from bottom of the lower bucket, into a slit you made in the top bucket. Then you dump the ground into the top bucket and fill up the bottom bucket. The water will now automatically go from the bottom bucket into the top bucket, making the ground wet. That leaves the top of the soil dry, which the mosquitoes don’t like. Another big advantage is that you only have to water them once in a while. I have one plant at home and the reservoir between the top and bottom bucket holds 8 liters of water. I water it once every other month or so.

      Example with pictures:

      (I don’t condone this specific product, it’s just as an example if you don’t understand what I’m talking about).

      2. Nematodes. You can buy nematodes that are like tiny worms (can’t see them with the naked eye), that eat the larvae. It works. It’s not cheap and they need to be fresh as they are living animals.

      3. cover the ground with a thick layer of sand. This dries the top soil, which they don’t like. Nice to combine this with step 1.

      1. @Bob said: “It’s caused by your ground being too moist, which attracts them. They lay eggs which then produce larvae that eat anything under the ground, including the roots of the plants.”

        Great answer Bob, thanks. I thought they were fruit flies. I did some more searching based on your info and found the pesky little buggers are often called Fungus Gnats (they’re not Mosquitoes).[1] Indeed moist soil with decaying organic material is where fungus gnats (and similar) thrive. Digging further in terms of gnat control, all your suggestions were good. In addition, many say placing traps out using a little apple cider vinegar and a few drops of dish soap can be quite effective.[2] There are many more suggestions out there on fungus gnat control – see [3] below.

        * References:

        1. Fungus Gnat

        2. Get Rid of Gnats With Apple Cider Vinegar – Complete Guide

        3. How to Get Rid of Fungus Gnats – The Ultimate Guide

        1. It’s funny. According to the Dutch wikipedia site, they are mosquitos. According to the English wikipedia site, they are flies. So we are both correct I guess.

          Apple cider doesn’t work against them. They work great against fruit flies. Mix water and apple cider vinegar 50/50 and add a single drop of dish soap in a cup and done. No need to cover it with plastic like some claim. I’ve been using that for a long long time as fruit flies are a plague in my area.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.